The present invention relates to low-fat food emulsions, particularly to low-fat oil-in-water emulsions, and to processes for preparing these emulsions.
Although an increasing number of consumers prefer low-fat food products over full fat food products, it is difficult for manufacturers of low-fat products to replicate the desired flavor and fatty mouthfeel of full-fat products. This difficulty is particularly a problem in low-fat oil-in-water emulsions such as dressings.
It has been demonstrated that lowering the fat content of foods gives rise to flavor imbalance, as the rate of flavor release is greater in fat-reduced foods; in this respect, reference is made to an article by Shamil et al in Food Quality and Preference 1991/2, 3 (1) 51-60 entitled xe2x80x9cFlavor release and perception in reduced-fat foodsxe2x80x9d.
The greater rate of flavor release in reduced-fat oil-in-water food emulsions is demonstrated by the present inventors in FIG. 1, which is a graph of profiles of flavor intensity against time for dressings having different levels of fat (see line 1 (traditional zero fat dressing) and line 2 (traditional 55 wt % fat dressing)).
During oral processing, full-fat (eg 55 wt % fat) dressings exhibit a gradual build up of flavor to a low peak of maximum flavor impact, followed by a slow dissipation of flavor. In contrast, traditional very low-fat/zero-fat (0.85% fat) dressings exhibit a rapid dissipation of flavor creating a very high peak of maximum flavor impact at an early stage of oral processing.
The profile exhibited by full-fat dressings equates to a taste and mouthfeel that are preferred by consumers: the profile exhibited by low-fat dressings equates to a flavor which is initially too intense, with no pleasing aftertaste.
Many important flavor molecules are lipophilic and hydrophobic. As fat levels are reduced in oil-in-water emulsions, a greater proportion of these flavor molecules are found in the water phase. When the emulsion is broken down, eg in the mouth during eating, the hydrophobic nature of the flavor molecules results in their rapid release into nasal airspace.
Developments in flavor technology have resulted in flavor molecules being encapsulated to control flavor release and to stabilise and protect the molecules. Commonly-used encapsulation techniques include spray-drying, bed fluidisation and coacervation. (See the reference xe2x80x9cEncapsulation and Controlled Releasexe2x80x9d by Karsa and Stephensen, Royal Soc Chem, ISBN 0.85/86-6/5-8.)
These techniques involve entrapping a flavor molecule within a covering or microcapsule. The resulting encapsulated product is often in the form of small dry particles, which are added to foodstuffs. Upon heating or eating the foodstuffs, the particles are thermally or physically broken down to release the flavor molecules. The release is normally rapid.
U.S. Pat. No. 5,498,439 discloses encapsulating flavor oils in a colloid gel, which is made from water and animal protein polymers or plant polysaccharides. The flavor oil is mixed with the gel components under high shear pressure to create a stable colloid gel matrix, in which the flavor oil is physically encapsulated and retained by the hydrophilic nature of the gel. A solution of the encapsulated flavor oil may be injected into meat to impart flavor thereto.
Co-pending application PCT/EP98/00645 (WO98/34501) describes non-frozen, low fat food emulsions having a delayed flavor release. In this reference, delayed flavor release is achieved by preparing biopolymer gel particles which contain small oil droplets containing flavor molecules. A delayed flavor release was obtained. The delayed flavor release was found to be due to (hindered) diffusion due to the presence of the gel biopolymer material surrounding the oil droplets containing a large proportion of the flavor molecules. The particles remained (to a large extent) intact for 60 to 90 seconds after consumption.
Although the solutions as proposed in PCT/EP98/00645 are for many purposes satisfactory in terms of delayed flavor release, it still leaves the desire for a solution for achieving more control on the flavor release pattern for some applications.
The present invention seeks to provide a low-fat food emulsion having a rate of flavor release which is more comparable to that of a full-fat food emulsion (than to the release rate found in traditional low/zero fat products) and which flavor release rate can be delayed and controlled, thereby creating a low-fat food emulsion having the texture and flavor of a full-fat food emulsion or novel flavor profiles different from those of zero or full fat products.
According to the present invention there is provided a low-fat food emulsion or dispersion comprising a continuous aqueous phase and a dispersed (or emulsified or suspended) phase which comprises fat particles, gel particles and fat-soluble flavor molecules, wherein at least 50% (but preferably substantially all) of the fat particles are located within the gel particles, and wherein at least 35% of the flavor molecules are located in a plurality of the gel particles to thereby delay the rate of release of the flavor molecules from the emulsion or suspension, and wherein at least part of the gel particles is gradually broken down in the mouth upon consumption, such that after 10 seconds after consumption the majority of the particles is still intact and 60 seconds after consumption at least the majority of the particles is no longer intact.
In the present invention, words like suspension, emulsion, or dispersion are used mixed, to describe the whole of the composition with in it the gelled particles. Although strictly speaking, as they are particles, they are suspended in the rest of the composition, and one should speak of a suspension. However, as they predominantly are made up of a gelled water phase (with in them oil droplets), this could also be regarded as an emulsion, which is why these words are also used herein to describe the system.
The actual amount of flavor molecules which is located in the gel particles will depend on the oil/water partition coefficient of the flavor molecules concerned. In the above, it is preferred that a plurality (i.e. more than 50%) of the flavor molecules are located in a plurality of the gel particles (which may be the case when the flavor molecule has a better solubility in oil than in water). The higher the percentage of the flavor molecules that is located in the gel particles, the better the delayed release is obtained.
For the purpose of the present invention, fat-soluble flavor molecules include flavor molecules which are totally soluble in fat or oil and flavor molecules which are only partially soluble in fat.
The gel particles are prepared from material comprising at least one food grade gel-forming biopolymer. The gel particles should be made such that they break down in the mouth upon consumption. This can be achieved by e.g. ensuring the particles are physically weak, so that they break down following shear forces that are present in the mouth. Weak particles can be obtained e.g. by using low concentrations of biopolymers when preparing them. Alternatively, the gel particles can be made from a material that breaks down following a trigger present in the mouth, e.g. gel particles from starch and/or derivatives thereof may be broken down by amylase present in the saliva, or particles made of gelatin may melt as a result of the temperature in the mouth. The biopolymer chosen for the gel particles may consist of a mixture and may also break down following a combination of break down triggers. An example of the latter are large, weak gelatin particles which break down following melting and as a result of shear forces. Starch, gelatin, agar (when used in low concentrations) and mixtures thereof are preferred biopolymers in this invention. Other biopolymers that could be used include carrageenan which can be made to melt close to mouth temperatures (via ion concentration and type), gellan, and pectin which could be made physically weak so that it breaks down under mouth shear, and CMC and Gum arabic which are used with gelatin to make coacervates which melt in the mouth. Casein gels can also be made to breakdown in the mouth via shear. Most preferred are starch and/or starch derivatives, gelatin and agar.
Mixtures of proteins and polysaccharides are preferred as they may interact associatively, dissociatively, or synergistically.
The low-fat-emulsion of the present invention may comprise between 0 and 30 wt % fat. Preferably the amount of fat is less than 10 wt % fat, more preferably less than 5 wt % fat. In a preferred embodiment, the emulsion comprises at least 0.01 wt % fat, more preferably at least 0.5 wt %. Emulsions having less than 3 wt % fat are also preferred: this very low level of fat are legitimately described as fat-free or zero-fat in many countries.
For the purpose of the present invention, the definition of fat includes liquid oil, crystallising fat blends and fat mimics such as sucrose polyesters.
When crystallising fat blends are used, enhanced control of flavor molecule transfer rates and additional textural benefits may be obtained.
The low-fat emulsion of the present invention may comprise from 0.1 to 99% by volume of gel particles, preferably from 5 to 50% by volume of gel particles. The gel particles may confer fat-like textural properties to the low-fat emulsion; in this respect, the emulsion preferably comprises from 20 to 99% by volume of gel particles.
The majority of the particles range in size from about 500 microns to about 8000 microns.
In the present invention it is believed that the profile of the flavor release is for the first few seconds (e.g. 10) is mainly diffusion controlled. If the material of the gel particles is well chosen, the rate of the flavor release is thereafter controlled by the speed of breakdown of the particles, in which their break down is described above. Usually, at 10 seconds after the microstructured emulsion (foodstuff) containing the emulsion is put in the mouth a minority is broken down. Over time, more and more particles break down causing a steady release of flavor molecules. After about 60 seconds, the majority of the particles is usually fully broken down. By chosing the material and size of the particles, the person skilled in the art can design the desired release profile, depending on the intended use.
The inventors of the claimed emulsion were surprised to find that the presence of gel particles delays the release of flavor molecules; this is surprising because the flavor molecules are of a size suitable for diffusing through the gel matrix of the particles. It is therefore understood that, in the present invention, the gel particles do not encapsulate the flavor molecules in the traditional sense, since the flavor molecules are not trapped within the gel particles.
Without wishing to be bound by theory, the inventors believe that the gel particles act as a static region within the mobile aqueous phase of the emulsion. When the emulsion is eaten, the aqueous phase is rapidly swept by oral fluids such as saliva, so that the flavor molecules are released very rapidly providing a very high initial flavor intensity which rapidly becomes depleted. A flavor molecule located in a gel particle diffuses therethrough as normal. By the time it has reached the surface of the gel particle to be swept by the oral fluids, a delay has occurred. Hence, flavor molecules located in gel particles experience delayed release relative to flavor molecules in the aqueous phase. In the emulsion, the dispersed fat phase is normally in the form of liquid oil droplets located in the gel particles. As many important flavor molecules are lipophilic (fat-soluble) they have a preference for solubilising in the oil droplets. The rationale behind this approach is that in o/w emulsions the release of lipophillic flavors occurs in the sequence oilxe2x86x92waterxe2x86x92air. It is therefore possible to control the release of lipophillic flavors by creating barriers around the oil droplets which hinder their release into the aqueous phase. Microstructured emulsions do this by increasing the diffusional pathway and reducing the rate at which lipophillic flavors are released into the aqueous phase.
However, it has become apparent that particles that break down slowly during mastication (xe2x80x98mouth degradable particlesxe2x80x99) enable flavor release profiles to be obtained which exhibit very different flavor release profiles from thatof both traditional low- and high-fat products. By controlling the properties of the gel particles, the oral breakdown of the el particles can be controlled, and following this, the flavor release can be controlled.
In accordance with the present invention there is also provided a process for the preparation of a low-fat food emulsion comprising the steps of
a) admixing fat and a gel-forming biopolymer to form a first liquid phase
b) adding the first liquid phase to a second liquid phase which promotes gel formation of the biopolymer to form gel particles having particles of fat located therein
c) mixing the gel particles with an aqueous phase and fat-soluble flavor molecules to form an aqueous-continuous emulsion, wherein at least part of the gel particles is gradually broken down in the mouth upon consumption, such that 10 seconds after consumption the majority of the particles is still intact and 60 seconds after consumption at least the majority of the particles is no longer intact.
Optionally, the first liquid phase is emulsified prior to step b. In step b, the first liquid phase may be injected into the second liquid phase. Alternatively, in step b, the first liquid phase may be sprayed on to the second liquid phase.
The second liquid phase may have a lower temperature than the first liquid phase in order to effect gel formation. Alternatively, the second liquid phase may react with the biopolymer in the first liquid phase in order to effect gel formation.
An emulsion according to the present invention may also be prepared using one of the following processes.
1) Shear Gel Method
Heat and homogenise the emulsion ingredients to form an oil in water emulsion. Cool the emulsion under shear.
2) Multiple Emulsion Method
Heat and homogenise the emulsion ingredients to form an oil in water in oil (duplex) emulsion. Cool the emulsion under shear and remove the outer oil phase.
When preparing a low-fat emulsion in accordance with the present invention, flavor components need minimal rebalancing to account for the low phase volume of fat.
Also, critical flavors, which are normally fat-soluble and therefore particularly prone to uncontrolled release in low fat emulsions, are released according to their xe2x80x9cfull-fatxe2x80x9d timescale, thereby improving the perception of their flavor.
The present invention provides means for controlling the transfer rates, including the rate of release, of flavor molecules in an emulsion, thereby allowing manipulation of the flavor release profile of low-fat emulsions. It also provides means for manipulating the texture of low-fat emulsions. Hence, low-fat emulsions can be prepared which have the taste and mouthfeel of full-fat emulsions. The present invention achieves this without recourse to an encapsulating coating which must be heated or solubilised in order to release encapsulated flavors.
The present invention can be applied in the manufacture of products like spreads, dressings, mayonnaise, sauces, ice-cream (including water-ice) etcetera, and related products that are regarded as the products mentioned above; being low in fat (including those products that are regarded as zero fat, but still contain few percentages of fat).